*ainijaz

Probably from a western Indo-European or pre-Indo-European plant-name *yoyni- / *h₁oyni- with semantic variation between ‘rush, reed’ and ‘juniper’. Compare Proto-Celtic *yoyni-, continued by Middle Irish áin; Proto-Italic *joiniko-, continued by Latin iuncus; and Latin iūniperus, which may contain the same first element (de Vaan 2008: 313; Koch 2020: 152; Matasović 2009a: 437). De Vaan explicitly notes Old Icelandic einir and Swedish en as possible Germanic comparanda, while also judging the stem *yoy-ni- to look non-Indo-European; Matasović likewise regards the western distribution as suggestive of a substrate loan rather than inherited PIE vocabulary.

Kroonen (2013: 12) reconstructs Proto-Germanic *ainja- from pre-Germanic *h₁oy-n-yo-, perhaps ultimately connected with an acrostatic PIE n-stem *h₁óy-n- ~ *h₁éy-n-s, especially if Hittite 𒂊𒅀𒀭 (e-i̯a-an /eiyan-/) belongs here. The Anatolian comparison would improve the case for PIE inheritance, but without it the Italic–Celtic–Germanic distribution and the irregular plant-name semantics favor a western Wanderwort or substrate origin (de Vaan 2008: 313; Koch 2020: 152; Matasović 2009a: 437). A direct North Germanic borrowing from Latin iūniperus is possible but less economical than shared inheritance or borrowing from an older western plant-name.